JP3201638B2 - Optical fiber with variable focal length lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber with a variable focal length lens having an optical coupling lens with a variable focal length.

[0002]

2. Description of the Related Art FIG. 16 shows a conventional optical fiber with a lens. In this case, a single lens is fixed to the end of the optical fiber. Thus, the light from the light source at point A is focused on the tip of the optical fiber.

[0003]

However, the conventional optical fiber with a lens has a problem that when the point light source moves, the light from the point light source cannot be focused on the tip of the optical fiber. This will be described specifically. First, consider the case where light from the light source at point A is focused on the tip of the optical fiber. If the focal length of the lens is f, the distances s ₁ and s _{2 at} each point are 1 / s ₁ + 1 / s ₂ = 1 / f. Next, consider the case where the light source moves from point A to point A '. By moving the light source, the distance s ₁ ′ of each point,
Since s ₂ ′ is 1 / s ₁ ′ + 1 / s ₂ ′ = 1 / f, the imaging point moves to the point B, and light from the light source can no longer be focused on the tip of the optical fiber.

In this case, if the light from the light source is to be focused on the tip of the optical fiber, the lenses can be replaced one by one, but this is not practical. It is also possible to use a combination of multiple lenses, such as a camera lens, to adjust the focal position by mechanically changing the positional relationship of each lens.However, the presence of a mechanical mechanism makes the device larger. I do. Further, a liquid crystal microlens can be used, but such a liquid crystal microlens has a problem that it is difficult to manufacture and has a slow response.

Accordingly, an object of the present invention is to provide an optical fiber with a variable focal length lens, which is compact, can be easily manufactured, and has a high response.

[0006]

In order to solve the above-mentioned problems, an optical fiber with a variable focal length lens according to the present invention comprises a voltage generator, a refractive index fixing member made of an optical material having no electro-optical effect, and an electro-optical device. A light-collecting member whose refractive index changes according to the electric field strength by joining and forming a refractive-index changing member made of a material, and a voltage generated by a voltage generator is applied to the light-collecting member. An optical coupling member having electrode means for changing the focal length of the light-collecting member, and an optical fiber having an end aligned with the optical axis of the optical coupling member, wherein the refractive index fixing member is excited by current. A semiconductor laser amplifier, wherein an optical coupling member also serves as an optical amplifier.

[0007]

According to the above-mentioned optical fiber with a variable focal length lens, the electrode means changes the focal length of the light collecting member by applying a voltage from a voltage generator to the light collecting member made of an electro-optical material. Therefore, the focal length can be easily and quickly adjusted only by operating the voltage from the voltage generator.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be briefly described below with reference to the drawings.

FIG. 1 is a diagram showing a cross section of an optical fiber with a variable focal length lens according to a first embodiment. Optical fiber 2
The holder 4 is fixed to the tip of the. An optical coupling device 6 is fixed in the holder 4 while being aligned with the optical fiber 2. The optical coupling device 6 includes a light collecting member 6a,
6b, and a pair of transparent electrodes 6c and 6d formed on both surfaces of the light collecting members 6a and 6b. The condensing members 6a and 6b are formed by bonding a convex lens-shaped member 6a formed of an electro-optical material whose refractive index changes by an electric field and a concave lens-shaped member 6b formed of a non-electro-optical material whose refractive index does not change. ing. Also, the transparent electrode 6c,
To 6d, a controlled voltage from a variable voltage source is applied to the left and right in the drawing, that is, in the optical axis direction of the optical coupling device 6, and changes the refractive index of the member 6a made of the electro-optical material.

The material of the member 6a is LiTaO ₃ ,
LiNbO ₃ , ZnTe, GaAs, a polymer, or the like can be used. As a material of the member 6b, a material having the same relative dielectric constant as the above material and a different refractive index can be used. In this case, the joint surface of each light condensing member has a constant curvature, and has a symmetrical shape about the optical axis of the optical coupling device 6 extending in the left-right direction in the drawing. In addition, the incident surface and the outgoing surface, which are both outer surfaces of each of the condensing members on which the transparent electrodes 6c and 6d are formed, are parallel to each other.

FIG. 2 is a view for explaining the operation principle of the optical fiber with a lens shown in FIG. Power supply 8 for transparent electrodes 6c and 6d
When an appropriate voltage V from the light collector is applied, the light condensing members 6a and 6b
Since the permittivity inside is uniform, the electric field inside it is uniform as E = V / d. In this case, the member 6 made of an electro-optical material
The refractive index n ₀ of a varies depending on the electric field intensity due to the Pockels effect. On the other hand, the refractive index n ₁ of the member 6b made of a non-electro-optic material does not change. Here, if the refractive index of the member 6a when no electric field is formed is n ₀ ′, then n ₀ = n ₀ ′ + Δn ₀ . Here, Δn ₀ = C · E (C: proportionality constant). Further, since the internal electric field E is uniform in proportion to the voltage V, the following relationship holds: Δn ₀ = C ′ · V (C ′: proportional constant). On the other hand, the focal length f ₀ of the member 6a is
Assuming that the curvature of the joining surface of the member 6a and the member 6b is R, 1 / f ₀ = (n ₀ -1) / R, and the focal length f ₁ of the member 6b is 1 / f ₁ = (n it can be expressed as ₁ -1) / R. Therefore, the members 6a and 6b
And the combined focal length, ie, the optical coupling device 6
The focal length f of, 1 / f = 1 / f 0 -1 / f 1 = (n 0 -n 1) / R = (n 0 '+ Δn 0 -n 1) / R = (n 0'-n 1 + C'V) / R. Therefore, since n ₀ ′, n ₁ , and R are constant, if (n ₀ ′ −n ₁ ) / R = a and C ′ / R = b, then 1 / f = a + bV. That is, the focal length f of the optical coupling device 6 can be arbitrarily changed by the voltage V from the power supply 8.

If the above-mentioned phenomenon is used, the focal length f of the optical coupling device 6 can be easily and quickly changed by the power supply voltage in accordance with the position of the point light source such as a light-emitting body or an object. The image of the light source can be focused on the end face of the optical fiber. Thus, light from the point light source can be coupled to the optical fiber 2 regardless of the position of the point light source. In this case, even when light is supplied from the end face of the optical fiber 2 to a point close to the end face, the irradiation position can be arbitrarily changed by changing the power supply voltage.

In the above description, the member 6a of the electro-optical material
Although the joining surface on the side is convex, it may be concave depending on the application. Although the relative permittivity of the member 6a made of the electro-optical material and the member 6b made of the non-electro-optical material are made equal, similar results can be obtained by using materials having different relative permittivity. For example, the non-electro-optical material may be air or vacuum, and the transparent electrode 6d may be formed in a thin film shape.

FIG. 3 shows an optical fiber with a variable focal length lens according to a second embodiment. FIG. 3A shows a perspective view thereof, and FIG. 3B shows a side view of the optical coupling device. In this case, the optical coupling device is different from the optical fiber with a variable focal length lens of the first embodiment. The optical coupling device 16 includes light collecting members 16a and 16b, and the light collecting members 16a and 16b.
Pair of electrodes 16c and 16d formed on both upper and lower sides of
It is composed of The light condensing members 16a and 16b are formed by combining a cylindrical member 16a made of an electro-optic material whose refractive index changes with an electric field and a cylindrical member 16b made of a non-electro-optic material whose refractive index does not change. ing. In this case, the left end face of the columnar member 16a protrudes into a lens shape having a constant curvature, and the right end face is flat. However, the 16b light incidence end face or the 16a light emission end face may have a curvature. Also, the electrodes 16c,
The upper and lower sides of the cylindrical member 16b on which 16d is formed are parallel to each other. A controlled voltage from the variable voltage source 8 is applied to the electrodes 16c and 16d in the vertical direction in the drawing, that is, in a direction perpendicular to the optical axis of the optical coupling device 16, thereby changing the refractive index of the member 16a made of an electro-optical material. In this case, the refractive index for light traveling in the optical axis direction can be changed by the electric field in the direction perpendicular to the optical axis, depending on the selection of the electro-optical material and the method of cutting out the crystal.

The operation of the optical fiber with a variable focal length lens shown in FIG. 3 will be described. In the illustrated optical fiber with a variable focal length lens, the refractive index of the main body of the cylindrical member 16a can be changed by the voltage applied to the electrodes 16c and 16d. As a result, the focal length f of the optical coupling device 16 can be appropriately changed, and light from the point light source can be easily transmitted to the optical fiber 2 regardless of the position of the point light source.
Can be combined. In this case, the electrode 16
It is not necessary to form c and 16d transparently. In addition, since no transparent electrodes are formed on the entrance surface and the exit surface of the optical coupling device 16, the transmittance can be increased optically ideally. Further, as in the first embodiment, the device operates even if the relative permittivity of the member 16a made of the electro-optic material and the member 16b made of the non-electro-optic material are different.

FIG. 4 is a view showing an optical fiber with a variable focal length lens according to a third embodiment. FIG. 4 (a) is a perspective view of the optical fiber, and FIG. 4 (b) is a side view of an optical coupling device. Also in this case, the optical coupling device is different from the optical fiber with a variable focal length lens of the first embodiment. The optical coupling device 26 includes light-collecting members 26a and 26b and a pair of transparent electrodes 26c and 26d formed on the input / output surfaces of the light-collecting members 26a and 26b.
It is composed of The light condensing members 26a and 26b include a Fresnel lens-shaped member 26a made of an electro-optical material,
It is formed by joining a member 26b made of a non-electro-optical material. In this case, since the amount of change in f does not depend on the thickness of 26a, the optical coupling device 26 can be formed in a thin film shape as shown in FIG. It operates without the non-electro-optic material 26b.

The operation of the optical fiber with a variable focal length lens of the third embodiment shown in FIG. 4 will be described. In the illustrated optical fiber with a variable focal length lens, the transparent electrodes 26c and 26c
f) The Fresnel lens-shaped member 26
The refractive index of a can be changed. The Fresnel lens simply acts as a lens, causing a change in f
This is Snell's law at the boundary between a and 26c. 26a
The refractive angle of light changes according to Snell's law with the change in the refractive index, and f changes. Thereby, the optical coupling device 26
Can be appropriately changed, and light from this point light source can be easily coupled to the optical fiber 2 irrespective of a change in the position of the point light source.

FIG. 6 shows an optical fiber with a variable focal length lens according to a fourth embodiment. Also in this case, the optical coupling device is different from the optical fiber with a variable focal length lens of the first embodiment.
The optical coupling device 36 is a condensing member 36 of a distributed index lens.
and a pair of transparent electrodes 36c and 36d formed on the input / output surface of the light-collecting member 36a. The light condensing member 36a is a rod lens made of a columnar electro-optical material, and its refractive index changes depending on the distance from the center of the optical axis. The refractive index increases as the distance from the center of the optical axis increases.
The focal length of the optical coupling device 36 changes depending on the manner of the refractive index distribution.

The operation of the optical fiber with a variable focal length lens of the fourth embodiment shown in FIG. 6 will be described. In the illustrated optical fiber with a variable focal length lens, the transparent electrodes 36c and 36c
The refractive index of the light collecting member 36a can be changed by the voltage applied to d. In this case, the material of the light-collecting member 36a, the method of cutting out the crystal axis, the impurity doping, and the like are adjusted so that the refractive index difference between the vicinity of the optical axis of the light-collecting member 36a and the periphery thereof decreases with an increase in the applied voltage. Accordingly, the focal length f of the optical coupling device 36 can be appropriately changed in accordance with the change in the refractive index of the light condensing member 36a, and the light from the point light source can be easily converted to an optical fiber regardless of the position of the point light source. 2 can be combined.

FIG. 7 is a diagram specifically illustrating the operation of the optical fiber with a variable focal length lens according to the fourth embodiment. As shown in the figure, the focal length of the optical coupling device 36 becomes longer as the voltage applied to the light collector 36a increases (0 → V ₁ → V ₂ ). In this embodiment, since only the electro-optic material is used and there is no need to join a non-electro-optic material,
Its manufacture is relatively simple compared to the first embodiment.

As described above, in the description of the fourth embodiment, an example has been shown in which the refractive index difference in the vicinity of and around the optical axis of the light collecting member 36a is reduced by applying a voltage. The light collecting member 36a can be formed as described above.
Further, in the above embodiment, the condensing member is described as a convex lens type having a positive refractive power. However, it is possible to use a condensing member having a negative refractive power and further combine it with another lens or the like. Further, similarly to the second embodiment, the voltage may be applied from a direction perpendicular to the light propagation direction.

FIG. 8 shows an optical fiber with a variable focal length lens according to the fifth embodiment. FIG. 8A is a perspective view of the optical fiber, and FIG. 8B is a side view of the optical coupling device. Also in this case, the optical coupling device is different from the optical fiber with a variable focal length lens of the first embodiment. The optical coupling device 46 includes a light collecting member 46a, a pair of transparent electrodes 46c and 46d formed on the input / output surface of the light collecting member 46a, and a lens 46e provided on the left side of the transparent electrode 46d in the drawing. Is done.
This condensing member 46a is made of a columnar uniform electro-optical material. The lens 46e is made of a two-dimensional Fresnel strip. The two-dimensional Fresnel strip has a transmission distribution concentrically, and the incident light is collected by diffraction.

The operation of the optical fiber with a variable focal length lens according to the fifth embodiment shown in FIG. 8 will be described. In the illustrated optical fiber with a variable focal length lens, the transparent electrodes 46c, 46
The refractive index of the light collecting member 46a can be changed by the voltage applied to d. That is, similarly to the principle of the third embodiment, the refractive index difference at the interface between the transparent electrode 46d and the light-collecting member 46a changes according to Snell's law, and the light-collecting member 46a
Changes the angle of incidence of the light. As a result, the optical coupling device 46
Can be reduced in accordance with an increase in the applied voltage, and light from this point light source can be easily coupled to the optical fiber 2 irrespective of a change in the position of the point light source.

In the above embodiment, the electro-optic material whose refractive index decreases as the applied voltage increases is used. However, a material whose refractive index increases as the applied voltage increases may be used. .

FIG. 9 shows an optical fiber with a variable focal length lens according to a sixth embodiment. In this case, the direction of the applied electric field is different from that of the optical fiber with a variable focal length lens of the sixth embodiment. The optical coupling device 56 includes a light collecting member 56a, a pair of electrodes 56c and 56d provided above and below the light collecting member 56a, and a lens 56e.
It is composed of The light collecting member 56a is made of a prismatic electro-optic material, and the lens 56e is made of a two-dimensional Fresnel strip.

The operation of the optical fiber with a variable focal length lens of the sixth embodiment shown in FIG. 9 will be described. In the illustrated optical fiber with a variable focal length lens, the refractive index of the light collecting member 56a can be changed by the voltage applied to the electrodes 56c and 56d. As a result of the change of the incident angle of the light to the light condensing member 56a, the focal length f of the optical coupling device 56 can be appropriately changed, and the light from the point light source can be easily changed regardless of the position of the point light source. It can be coupled to the optical fiber 2.

FIG. 10 is a view showing an optical fiber with a lens according to a seventh embodiment, and FIG. 10 (a) is a perspective view thereof, and FIG.
0 (b) shows the structure of the optical coupling device of FIG. 10 (a). In this case, the optical coupling device differs from the optical fiber with a lens of the first embodiment, and the focal length is changed by controlling the refractive index distribution. The optical coupling device 66 includes a light-collecting member 66a, a transparent electrode 66c formed on an input / output surface of the light-collecting member 66a,
66d. The light-collecting member 66a is made of a columnar electro-optic material, and has a material and a crystal axis that have a higher refractive index as the electric field is stronger. Further, the transparent electrode 66d on the incident surface side includes a plurality of concentric electrode elements, and each electrode 66d is connected to power supplies 8a to 8 of different voltages.
b.

The operation of the optical fiber with a lens according to the seventh embodiment shown in FIG. 10 will be described. In the illustrated optical fiber with a lens, the refractive index of the light collecting member 66a can be changed by the voltage applied to the transparent electrodes 66c and 66d.
In this case, each electrode 66d is connected to a power source 8a to 8d of a different voltage.
, And the voltage is higher at the center electrode 66d (V ₁ > V ₂ > V ₃ > V ₄ ). Therefore, the light-collecting member 66a has a distribution in which the refractive index increases as the refractive index approaches the optical axis depending on the distance from the optical axis. As a result, the incident light can be focused on the emission surface. here,
As the refractive index difference between its surrounding vicinity of the optical axis of the condensing member 66a is decreased, the voltage of the power supply _{8a~8d V 1, V 2, V} 3,
By adjusting V ₄ , the focal length f of the optical coupling device 66 can be appropriately changed in accordance with the change in the refractive index distribution of the light condensing member 66a. Can be easily coupled to the optical fiber 2.

Although FIG. 10 shows the case where an electric field is formed almost ideally, the refractive index distribution becomes smoother as it approaches 66c in the light traveling direction due to crosstalk or the like.
In some of the embodiments described above, when the electro-optical material constituting the optical coupling device is a semiconductor such as ZnTe or GaAs, the optical coupling device can also serve as an optical amplifier.

Hereinafter, some examples to which the optical fiber with a lens of the above embodiment is applied will be described as reference examples. FIG. 11 shows an application example of the optical fiber with a lens of the above embodiment, and is a diagram showing a device capable of automatically controlling the focal length of the optical coupling device. The same optical coupling device 106 as in the first embodiment is used. Light from the light source that shifts in the left-right direction in the drawing is collected by the optical coupling device 106 on the end face of the optical fiber 102 connected to the rear end face. The light incident on one end of the optical fiber 102 is split by a fiber coupler 108 connected to the other end. The light that has traveled straight through the fiber coupler 108 is output to the outside through an optical fiber 110. Fiber coupler 10
The light that has been partially branched at 8 passes through an optical fiber 112 and is converted into an electric signal by a photodetector 114. Control unit 11
6 is a pair of electrodes 106 provided on an input / output surface of the optical coupling device 106 based on an electric signal from the photodetector 114.
c, 106 d by controlling the voltage applied to
Adjust the focal length of 6. Specifically, the optical coupling device 10
The light amount coupled from the light source to the optical fiber 102 can be kept constant by adjusting the focal length of 6, or the maximum value of the light amount can be obtained and the output light can be held at this value.

FIG. 12 is a graph showing the operation of the apparatus of FIG. 11, and is a graph showing the relationship between the electrode control voltage V and the intensity of the output light during the operation of the apparatus. In this case, for example, by controlling the electrode control voltage to V ₀ , the optical coupling from the changing light source to the optical fiber can be maximized.

FIG. 13 shows an application example of the optical fiber with a lens of the above embodiment, and is a diagram showing an apparatus provided with an optical amplifier at an output stage. The same optical coupling device 106 as that of the fourth embodiment, the fifth embodiment and the like is used. Light from the light source is collected by the optical coupling device 106 on the end face of the optical fiber 102 connected to the rear end face. The light that has entered one end of the optical fiber 102 is amplified by a connected optical amplifier 120 provided at the other end and output to the outside. The optical amplifier 120 has a current-excited TWA
(Semiconductor optical amplifier), a rare earth doped fiber pumped by a semiconductor laser, or the like can be used. When a rare earth-doped fiber is used as the optical amplifier, the optical fiber 102 can also be used as the optical amplifier. Further, as a modification in the illustrated case, an optical amplifier 120 may be disposed between the optical fiber 102 and the optical coupling device 106.

As is apparent from the above description, the use of the optical amplifier 120 as described above is effective when the output of the optical fiber 102 is reduced, or when a sufficient optical output is desired at the subsequent stage. Become.

FIG. 14 shows a fiber camera to which the optical fiber with lens of the above embodiment is applied, and shows a device using a fiber bundle composed of a plurality of optical fibers as the optical fiber. Light from the object is imaged by an optical coupling device housed at the end of the cable 130 and coupled to the end face of the fiber bundle. In this case, cable 1
The voltage applied to the 30 end optical coupling devices is controlled by the focus controller 134. The light coupled to the fiber bundle is detected by the television camera 132 as an image of the object. The image of the object is enlarged and displayed on the monitor 136. In this case, the focus controller 134 can be controlled based on the output of the television camera 132.

FIG. 15 is a partial sectional view showing an enlarged view of the distal end of the cable 130. FIG. 15A shows a case where the same optical coupling device as that of the fourth embodiment is used, and FIG. )
(C) shows a case where an optical coupling device different from the above is used. First, the case of FIG. 15A will be described. In the flexible sheath 141, the fiber bundle 142 and the optical coupling device 146 are aligned and fixed. Light from the object is imaged on the rear end face by the optical coupling device 146. Each pixel of this image is individually transmitted for each optical fiber forming the fiber bundle 142 and detected by the television camera 142. The wiring 141 f for supplying a voltage to both electrodes 146 c and 146 d of the optical coupling device 146 is also provided in the sheath 141. According to the above-described device, an image of an object near the distal end of the cable 130 can be detected as two-dimensional information. However, in the case of the above apparatus, the coupling efficiency to the optical fiber is not good because the cladding of the optical fiber is much larger than the area of the core.

The optical coupling device shown in FIG.
It comprises a lens array 246 obtained by modifying the optical coupling device of FIG. A rod lens constituting a lens array 246 is connected to each optical fiber of the fiber bundle 142. Each rod lens has a tapered core whose core diameter decreases toward the fiber bundle 142. The use of such a lens array 246 improves the coupling efficiency. By increasing the coupling efficiency in this way, the capability of detecting an image of an object can be enhanced even in a dark place, and application to fields such as an endoscope becomes possible. However, when used for an endoscope, a coating such as insulation is required so that the voltage applied to the lens array 246 is not applied to the inside of the body. Further, when it is required that the entire diameter of the optical fiber bundle is small in application to a field such as an endoscope, the optical fiber bundle 142 is used.
It is preferable to use a tapered optical fiber in which the diameter of each optical fiber gradually decreases in the light traveling direction, and gradually increases in the extracorporeal part.

The optical coupling device shown in FIG.
This is a lens in which the lens of FIG. Each lens 246, 346 has substantially the same configuration as 146, and is controlled by independent power supplies 350a, 350b. By using such two-stage lenses 246 and 346, an optical system that cannot be constituted by one lens, such as a zoom lens, can be formed at the end of the fiber bundle 142.
With such an apparatus, an image can be observed with a variable magnification.

[0038]

As described above, according to the optical fiber with a lens according to the present invention, the electrode means applies the voltage from the voltage generator to the light-collecting member made of the electro-optical material, thereby forming the light-collecting member. Since the focal length is changed, the focal length can be easily and quickly adjusted only by operating the voltage from the voltage generator.
In addition, since the focal length of the light collecting member is changed only by adjusting the voltage applied to the electro-optical material, the device itself can be downsized.

[Brief description of the drawings]

FIG. 1 is a diagram showing the structure of an optical fiber with a lens according to a first embodiment.

FIG. 2 is a diagram illustrating the operation of the first embodiment.

FIG. 3 is a diagram showing the structure of an optical fiber with a lens according to a second embodiment.

FIG. 4 is a view showing a structure of an optical fiber with a lens according to a third embodiment.

FIG. 5 is a diagram showing a modification of the optical coupling device constituting the optical fiber with a lens of FIG. 4;

FIG. 6 is a diagram showing a structure of an optical fiber with a lens according to a fourth embodiment.

FIG. 7 is a diagram for explaining the operation of the first embodiment.

FIG. 8 is a diagram showing a structure of an optical fiber with a lens according to a fifth embodiment.

FIG. 9 is a diagram showing a structure of an optical fiber with a lens according to a sixth embodiment.

FIG. 10 is a view showing the structure of an optical fiber with a lens according to a seventh embodiment.

FIG. 11 is a diagram showing an application example of the optical fiber with a lens according to the embodiment.

FIG. 12 is a view for explaining the operation of the apparatus in FIG. 11;

FIG. 13 is a diagram showing another application example of the optical fiber with a lens according to the embodiment.

FIG. 14 is a diagram showing another application example of the optical fiber with a lens according to the embodiment.

FIG. 15 is a diagram showing a structure of a main part of the optical fiber with a lens shown in FIG. 14;

FIG. 16 is a diagram showing the structure of a conventional optical fiber with a lens.

[Explanation of symbols]

2 ... optical fiber, 6 ... optical coupling means, 6c, 6d ... electrode means.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-105117 (JP, A) JP-A-61-35407 (JP, A) JP-A-61-156221 (JP, A) JP-A-61-156221 160715 (JP, A) JP-A-2-42401 (JP, A) Japanese Utility Model Application 60-6098815 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/24-6 / 43 G02F 1/03 G02F 1/29-1/295 H01S 3/00-3/30 H01S 5/00-5/50

Claims (1)

(57) [Claims] 1. A refraction element according to an electric field intensity, which is formed by joining a voltage generating device, a refractive index fixing member made of an optical material having no electro-optical effect, and a refractive index changing member made of an electro-optical material. A light-condensing member having a rate changing, and an optical coupling member having electrode means for changing a focal length of the light-condensing member by applying a voltage generated by the voltage generator to the light-condensing member, An optical fiber having an end aligned with the optical axis of the optical coupling member, wherein the refractive index fixing member is a current-excited semiconductor laser amplifier, and the optical coupling member also serves as an optical amplifier. Characteristic optical fiber with variable focal length lens.